payment_queryInfo

Estimates the fee for an extrinsic on Kusama.

Use Cases

• Fee estimation - Calculate transaction costs before sending
• UI display - Show fees to users for parachain experimentation, early feature deployment, and production-grade testing with real value
• Transaction planning - Ensure sufficient funds

Parameters

Parameter	Type	Required	Description
extrinsic	String	Yes	Hex-encoded unsigned extrinsic
blockHash	String	No	Block hash for fee calculation

Request

{
  "jsonrpc": "2.0",
  "method": "payment_queryInfo",
  "params": ["0x..."],
  "id": 1
}

Returns

Field	Type	Description
weight	Object	Transaction weight
class	String	Dispatch class
partialFee	String	Estimated fee

Code Examples

cURL

curl  \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "payment_queryInfo",
    "params": ["0x..."],
    "id": 1
  }'

JavaScript

import { ApiPromise, WsProvider } from '@polkadot/api';

const provider = new WsProvider('');
const api = await ApiPromise.create({ provider });

// Create transfer (unsigned for estimation)
const transfer = api.tx.balances.transfer('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY', 1000000000000);

const info = await transfer.paymentInfo('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY');
console.log('Partial fee:', info.partialFee.toHuman());

await api.disconnect();

Related Methods

• author_submitExtrinsic - Submit transaction